1. Field of the Invention
The present invention relates to computer graphics (CG) and, more particularly, to a method and device for rendering a stereo model arranged in a virtual three-dimensional space, and its contour, and a computer-readable recording medium stored with a rendering program.
2. Description of Related Art
In recent years, the non-photorealistic rendering technique has been investigated in the field of CG. This non-photorealistic technique is intended to express a hand-written image with CG. As this technique, there have been a variety of image forming techniques for correctly drawing a contour of a stereo model automatically, even when the states of a viewpoint position or a direction of sight line, or the arrangement, direction or shape of the stereo model are changed. The stereo model is exemplified by a 3D object expressing a human-shaped character. This stereo is composed of a plurality of polygons, for example.
In the technique disclosed in Unexamined Published Japanese Patent Application No. 7-85310, for example, it is decided at first whether or not the individual sides of polygons composing a stereo model belong to the contour portions sides of polygons composing a stereo model belong to the contour portions. Then, the sides decided as the contour portions are drawn as the contour. In Unexamined Published Japanese Patent Application No. 7-160905, on the other hand, there is disclosed a technique for drawing the contour by employing the pixels in a display image to be rendered from the stereo model as a unit and by detecting whether or not the individual pixels belong to the contour portions.
In order to draw the contour, according to the prior art, it is necessary to detect the contour portions by decomposing the stereo model into the side units of polygons or the pixel units to be rendered. This makes the processing complicated for drawing the contour.